New research finds that a shift in diet to incorporate more fiber could encourage specific types of gut bacteria, reducing the symptoms of diabetes and aiding weight loss.

Type 2 diabetes is often referred to as a lifestyle disease; in many cases, it can be prevented by changing habits such as diet and activity levels.

However, modern society seems powerless to halt its onward march.

Diabetes now affects almost 1 in 10 people in the United States. Currently, more than 100 million adults in the US have diabetes or prediabetes.

The condition impacts levels of glucose in the body, meaning they can no longer be regulated correctly, leading to damage of tissues and organs.

The hormone at the root of this dysfunction is insulin. People with type 2 diabetes either produce too little or their bodies do not respond adequately to it.

Because the type 2 juggernaut does not appear to be slowing, uncovering new ways to intervene is of paramount importance. Of course, prevention is the end goal where possible, but for those living with the condition, controlling it is also vital.

In recent years, gut bacteria have been brought in for questioning. Could they hold some answers?

Gut bacteria and diabetes

The human gut contains billions of bacteria—some good for health, some not so good. Overall, they are essential to the proper functioning of the digestive system, and, as it is slowly being revealed, they are influential across many of the body's systems.

Previous studies have shown that people who consume more fiber have a lower risk of developing type 2 diabetes. A diet rich in fiber can also help to reduce fasting glucose levels in those already living with diabetes. However, individual responses to this type of dietary intervention have been variable.

Recently, Liping Zhao—who is a professor at Rutgers University-New Brunswick in New Jersey—studied the fiber-gut bacteria-diabetes relationship in more detail. He wanted to understand how a fiber-rich diet might influence gut flora and reduce symptoms; once the mechanism is understood, it will be easier to design tailored anti-diabetes diets.

The study, which ran for 6 years, is published this week in the journal Science.

Many gut bacteria types break down carbohydrates into short-chain fatty acids, including acetate, butyrate, and propionate. These fatty acids help to nourish the cells that line the gut, reduce inflammation, and regulate hunger.

Earlier studies have found an association between reduced levels of short-chain fatty acids and diabetes, among other conditions.

In the new study, the team put the participants on one of two diets. Half received standard dietary recommendations, and the others consumed a similar diet but with the inclusion of high levels of several dietary fibers, including whole grains and traditional Chinese medicinal foods.

The experimental diet also included prebiotics, which encourage the growth of gut bacteria that make short-chain fatty acids. Both groups were controlling blood sugar with the help of a drug called acarbose.

Which bacteria are important?

After 12 weeks, participants on the high-fiber diet demonstrated a larger reduction in their 3-month average blood glucose levels. Also, their fasting blood glucose levels dropped quicker, and they lost significantly more weight than the control group.

Next, Zhao and colleagues wanted to distinguish which strains of bacteria were responsible for this positive effect. Of the 141 gut bacteria strains capable of making short-chain fatty acids, just 15 are promoted by the consumption of fiber. Levels of these were found to correlate with the level of healthy changes.

"Our study lays the foundation and opens the possibility that fibers targeting this group of gut bacteria could eventually become a major part of your diet and your treatment."

Liping Zhao

When these strains became the dominant species in the gut, they increased levels of the short-chain fatty acids butyrate and acetate. The researchers believe that these compounds create a more acidic environment in the gut, which reduces the numbers of unwanted bacterial species, leading to an increase in insulin production and "better blood glucose control."

These new findings lay the groundwork for designing innovative diets that could help people with diabetes to manage their condition through the food that they eat.

As the number of US individuals with diabetes steadily grows, this type of simple, relatively cheap intervention could make a huge difference to people's quality of life.